Antigen-specific antibody quantification will be required for Influenza and Hepatitis B antigens that are vaccine components, as well as non-vaccine Influenza antigens to define cross-reactivity. Measurements for standardized hepatitis B vaccine antigens will be through medical service providers. However, a careful and thorough definition of influenza antigens is central to this proposal. The core will have to accurately quantify serum antibody titers against: i) Flu vaccine component antigens, ii) Flu non-vaccine component antigens, and iii) hemagglutinins from different Flu strains. This core will support the U19 program through four aims: Aim 1: Quantification of antigen-specific antibodies and antigen-specific B cells. The core will measure with high fidelity serum antibodies against Influenza antigens. This will support Project 1, 2, 3, 4, and 5. Aim 2: Characterization of anti-Influenza neutralizing antibodies. The core will score neutralizing anti- Influenza serum antibody levels and appraise their cross-reactivity. This will support Project 1, 2, 3, 4, and 5. Aim 3: Measurement of serum cytokine and chemokine levels. The core will measure the levels of multiple cytokines and chemokines in sera and culture supernatants. This will support Project 1,2,3, 4, and 5. Aim 4: Detection of antibodies against self antigens. The core will perform proteome-wide surveys of auto-antibodies for Project 3. This will support Project 4. Aim 5: Development of novel biomarker detection reagents. The core will develop novel protein and antibody-based biomarkers for validation of discoveries made through all the Project areas. This will support Project 1, 2, 3,4, and 5.